Known rotary valves have included rotors with slots in a face thereof to provide communication between flow passageways in the body of the valve. Because a large separating force between the rotor and the body is created by fluid as it flows through the slots, a large force is required for sealing the rotor and the body to prevent leakage.
Typically, the rotor abuts directly against the body of the rotary valve. Misalignment of the rotor and the body can cause ununiform wear of the sealing surfaces therebetween. Due to irregularities in the sealing surfaces of the rotor and the body caused by wear, the surfaces do not exactly conform to one another resulting in leakage during both rotation of the rotor and while the rotor is stationary.
Known rotary valves typically include a stepper motor which rotates the rotor into alignment with various flow passageways of the body wherein positioning of the rotor is accomplished by monitoring the number of electrical drive pulses applied to the motor. This method does not provide positive positioning of the rotor with respect to the body of the valve and has been found to be unreliable.